PERMIAN BASIN. The Permian Basin is located in West Texas and the
adjoining area of southeastern New Mexico. It underlies an area approximately
250 miles wide and 300 miles long and includes the Texas counties of Andrews,
Borden, Crane, Dawson, Ector, Gaines, Glasscock, Howard, Loving, Martin,
Midland, Pecos, Reeves, Terrell, Upton, Ward, and Winkler. The name
derives from the fact that the area was downwarped before being covered by
the Permian sea and the subsidence continued through much of the Permian
period; consequently, it contains one of the thickest deposits of
Permian rocks found anywhere. Although it is structurally a basin in the
subsurface, much of the basin lies under the Llano
Estacadoqv and the northwestern portion of
the Edwards Plateau,qv which are topographically
high. On the west and south it extends across the Pecos River valley to mountain
ranges in both New Mexico and West Texas.

The presence of rocks of Permian age was first reported by George G. and
Benjamin F. Shumardqv in 1858 after a study
of outcrops in the Guadalupe Mountains. Later work in West Texas by Johan
August Uddenqv and his associates in the
Bureau of Economic Geology at the University of Texas contributed to knowledge
of the age, structure, and stratigraphy of sediments found in outcrops around
its Texas margin. When the Permian sea retreated southward, it left the Permian
Basin area with a restricted outlet. This resulted in an inland sea where
evaporation greatly exceeded fluid intake, and a great thickness of "evaporite"
sediments was deposited; one of these was potash, a critical commodity during
World War I,qv until then a product obtained
from Germany. Udden's early investigations led the United States Geological
Surveyqv to concentrate much of its early
effort in the search for potash in this area. The first commercial deposit
was found in New Mexico in 1925. Up to 1967 all seven of the potash companies
operating in the Permian Basin, representing an investment of some $200 million,
were located in New Mexico. Texas deposits have not been developed because
of the more expensive processes involved.

Much of the Permian Basin was home to the Comanche Indians until they were
finally forced out by the United States Army in 1875. Because of good grasslands,
most of the area was inviting to both ranchers and farmers. Since surface
water was almost nonexistent, ranchers and farmers drilled water wells to
sustain themselves and their livestock, and they often found evidence of
oil or gas. The first commercial oil well in the Permian Basin was completed
in 1921 in Mitchell County, on the east side of the basin; completed at a
total depth of 2,498 feet, it was the discovery well of the Westbrook field.
Early oil prospecting was started in southeastern New Mexico about the same
time as in West Texas. By 1923 it was presumed that the Permian Basin was
in the form of an elliptical bowl, the subsurface strata dipping from the
rim to a maximum depth in the middle. Because of this and the lack of suitable
rock outcrops in the interior during the early search for oil, geological
survey crews looked for surface anticlines in the Edwards Plateau and the
rock outcrop areas west and south of the Pecos River. This method resulted
in the discovery of several good oilfields, notably the World field in Crockett
County, the McCamey field in Upton and Crane counties (1925), and the Yates
oilfieldqv in Pecos County (1926). Prior
to the Hobbs field discovery in 1928, all discoveries were made as a result
of random drilling or surface and subsurface mapping. The Hobbs field discovery
was made after magnetometer and torsion balance surveys both showed the area
to be anomalous. From that time on geophysics, particularly the seismograph,
was used as an exploratory tool. By 1929 a sufficient number of oil tests
had been drilled to give sketchy control for a subsurface map of the Permian
Basin. Its outline was fairly well defined, and oil discoveries within the
basin suggested the probability of interior folds. In 1930 Lon D. Cartwright
published a report with a cross section and map, showing a large positive
area located in the approximate middle of the basin, which he named the Central
Basin Platform. The map showed the platform trending north­northwest
across the Texas-New Mexico line into Lea County. By this time a sufficient
number of wells had been drilled to show that the Central Basin Platform
was a structural feature common to both states.

Because of the great distances to the markets and the lack of pipelines through
which to move the oil, deep tests were not economically justified. Consequently,
all oilfields discovered before 1928 were producing from Permian dolomite
or sand, from depths less than 4,500 feet. A deep test was started in the
Big Lake oil fieldqv in Reagan County, and
in 1928 a large flow of oil and gas was encountered at 8,525 feet.
Fossil evidence showed the producing section to be of Ordovician age.
This discovery greatly expanded the prospects for the Permian Basin's becoming
a major oil and gas producing area; however, because of the Great
Depressionqv in the early 1930s few locations
for deep tests were made prior to 1936. With the coming of World War
IIqv the need for oil was urgent, and it
became economically justified to drill more and deeper tests. During the
war many new oil and gas zones were found not only in rocks of Permian
and Ordovician age but also from zones in each geologic system from Permian
through Cambrian and from practically every known type of subsurface
trap. Two of the largest accumulations were the Horseshoe Atoll
and the Spraberry trend area. Horseshoe Atoll is a subsurface accumulation
of fossiliferous limestone, as much as 3,000 feet thick, deposited during
Pennsylvanian and early Permian time in the northern part of the Midland
basin in West Texas. It is a horseshoe­shaped mass about ninety miles
across and seventy miles from north to south. The crest of the atoll is a
series of irregular hills and depressions. Oil migrated to many of these
buried hills and was trapped in the porous rock, resulting in a line of oilfields
nearly 200 miles in length. The Spraberry trend area is located in the region
between the south end of the Llano Estacado and the north part of the Edwards
Plateau (see SPRABERRY-DEAN SANDSTONE FIELDS). The producing structure
here is basically a fractured permeability trap on a homoclinal fold about
150 miles in length. Oil production is practically continuous along its entire
length; its maximum width is thirty­five miles.

The entire Permian Basin during 1966 produced a total of 607 million barrels
of oil and 2.3 trillion cubic feet of gas for a total of $2 billion. A cumulative
total of 11.3 billion barrels of oil had been produced. Intrastate and interstate
gas pipeline systems were expanded throughout the area, and Midland­Odessa
was the headquarters for the oil and gas
industryqv in the Permian Basin area. Hundreds
of millions of dollars have been spent on petrochemical refineries and
supplemental construction work in the Permian Basin, which was rated the
largest inland petrochemical complex in the United States. Some of the more
commonly known Permian Basin petrochemical products were synthetic rubber,
plastics, emulsion paints, solvents, food wrappers, nylon, ammonia, nitric
acid, hydrogen, and fertilizer. In 1992 the Texas counties of the Permian
basin produced over 217 million barrels of oil. Total production for that
region up to the beginning of 1993 was over 14.9 billion barrels. See
alsoPETROCHEMICAL INDUSTRY.